greetings to the forum, I have a bavaria 36 with a volvo md2030 and I have observed that there are two aft tubes that I assume are to ventilate the engine cabin with air, one of the tubes has an engine that I think is the tube that extracts air of the engine and the other I think is the air intake tube of the engine. However when I start the engine and put my hand on the stern tube outlets I don't get any air movement. If my observations are correct, the questions I have are; When is the exhaust fan activated? What mechanism activates it? How can i check that it works?